26 November 19

What direction does the Evaporation Duct refract RF signals

  1. Horizontal following the curvature of the earth
  2. Horizontal
  3. Horizontal up and down following the curvature of the earth 
  4. Horizontal parallel to the earth’s curvature

Answer is “3”… The drop in the refractive index of the atmosphere within the first few meters above the surface of the sea causes incident radio waves to be refracted towards the earth more than normal so that their radius of curvature becomes less than or equal to that of the earth’s surface. The sudden change in the atmosphere’s refractivity at the top of the duct causes the radio waves to refract back into the duct, and when it comes in contact with the surface of the sea, it gets reflected upwards again.

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